As is well known in the art, alkylamines can be prepared by reacting an alkanol with ammonia in the presence of hydrogen over a hydrogenation catalyst. The alkylamine products which are usually less volatile than ammonia or hydrogen can be condensed prior to effecting a separation between the unreacted ammonia and hydrogen. It is often the case that both the ammonia and the hydrogen streams are recycled to the amination reactor, but the formation of hydrocarbons as a by-product of the reaction contaminates the hydrogen stream and requires that the hydrogen and these by-products be vented to control hydrocarbon build-up. For example, in processes for the preparation of monoisopropylamine and diisobutylamine, hydrocarbons are produced to the extent that they must be removed from the hydrogen vent stream if hydrogen is to be recycled to the amination reaction. Increasing cost for hydrogen over the past several years makes it desirable to recover the hydrogen from the gaseous vent for recycling.
U.S. Pat. No. 2,365,721 discloses the preparation of amines by reacting C.sub.2 -C.sub.8 alkanols with ammonia in the presence of hydrogen over a hydrogenation catalyst. The amine products which are less volatile than ammonia are condensed and separated from the ammonia and hydrogen which is then passed through an activated charcoal adsorber to remove any less volatile reaction products along with part of the ammonia. The remaining ammonia and hydrogen are then recirculated with a further quantity of the alkanol to the reaction.
U.S. Pat. No. 3,420,828 discloses a process for producing N-methoxyethylmorpholine in which the reaction product stream is separated in a separator to provide for the removal of hydrogen as an overhead for recycling to the reactor.
U.S. Pat. No. 3,710,715 discloses a process for the production of methylamines by the ammonolysis of methanol in the vapor phase. The process stream from the reactor is cooled and residual hydrogen and a small amount of ammonia are flashed off in a flash drum for recycling.
U.S. Pat. No. 4,310,697 describes a process for the preparation of dimethylethylamine by the reaction of ethanol with dimethylamine in the presence of hydrogen and a hydrogenation/dehydrogenation catalyst. The gaseous reaction effluent is cooled in a series of water-cooled condensers and then separated in a separator to provide a liquid product stream and an uncondensed gas stream of essentially hydrogen and 1 to 2% dimethylethylamine. The gas stream is recycled to the reactor after passing through an absorption column which can function either as a washer (by spraying the gas loaded with amine with water or ethanol), or to rid the gas of all liquid particles.